I am designing a PoE powered development board with an ESP32 microcontroller module.
I am using the following circuit for the PoE power supply:
This is a direct copy of the PoE power circuit used by Olimex on their ESP32-POE boards.
Obviously, the behaviour I expect is a working ethernet connection regardless if the device is powered through the ethernet port or not and that the device will power on when connecting it to a PoE switch or injector.
The actual results I am seeing are the following:
When connecting to a non PoE switch with other power source: There is a reliable ethernet connection and everything works as expected.
When connecting to a PoE switch without other power source for the device: The device does not power on at all. Very low voltage (milli volts) measured from power traces on the PCB.
When connecting to a non PoE switch through a PoE injector: The device powers on and the activity LED on the switch and the device both turn on. The Link light blinks on the device but not the switch. The device does not receive an IP from the DHCP server and if I set a static IP, I still cannot establish any kind of connection to the device.
My thoughts on these symptoms:
Since the device does not turn on at all when connected to a PoE switch, It seems like the classification isn't working. It is however working for the PoE injector. When the device gets power from the ethernet port, there might be interference that disturbs the ethernet signals. Is this possible? I can provide a screenshot of the PCB traces if necessary.
Does anyone else have any insights on these symptoms and what the cause might be?
Edit 1: The data sheets for the ICs: